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Date: Mon, 10 Mar 2003 11:05:25 +0100
To: Con Kolivas <kernel@kolivas.org>,
       linux kernel mailing list <linux-kernel@vger.kernel.org>
From: Mike Galbraith <efault@gmx.de>
Subject: Re: 2.5.64-mm2->4 hangs on contest
Cc: Andrew Morton <akpm@digeo.com>
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At 08:12 PM 3/10/2003 +1100, Con Kolivas wrote:
>On Mon, 10 Mar 2003 18:05, Mike Galbraith wrote:
> > At 01:29 PM 3/10/2003 +1100, you wrote:
> > >Tried running contest on 2.5.64-mm2 and mm4 and had the same thing happen.
> > > It will hang reliably during process_load. I tried not running
> > > process_load but it would still get stuck in one of the other loads
> > > (either a tar load or list load). I can simply stop contest at that stage
> > > but then the machine wont work well hanging at the console after a minute
> > > or so. This started at mm2 (doesn't happen with mm1).
> > >
> > >Here is the sysrq-p and sysrq-t output during process_load (which hangs
> > > every time):
> >
> > hmm, the below looks interesting to me...
> >
> > >ksoftirqd/0   R C129A000     2      1             3       (L-TLB)
> > >Call Trace:
> > >  [<c0118f3e>] ksoftirqd+0x5e/0x9c
> > >  [<c0118ee0>] ksoftirqd+0x0/0x9c
> > >  [<c0106f1d>] kernel_thread_helper+0x5/0xc
> >
> > I see that too with irman.  You could try renicing the shell you start
> > contest from to >= +12.  With irman, what appears to be cpu starvation
> > ceases to be a problem at exactly +12.  I also see kapmd constantly wanting
> > to run but not being serviced.
>
>Contest uses a modified process load from irman so it exhibits similar
>behaviour. Not sure what +12 actually tells me though :-(

Aha!  No wonder your symptoms look so similar.  +12 is just a magic number 
that works... found by trusty old trial and error method.  What I wanted to 
see was if your hang would also go away with the same magic number, or if 
renicing with any value helped you at all.

>My simplistic understanding is that the pipe task in process_load gets
>constantly elevated as "interactive" by the new scheduler, and nothing else
>ever happens.

Appears so.  I can make it "work" by doing a dinky (butt ugly:) tweak in 
activate_task().

         -Mike 

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